In a line for conditioning a product in receptacles, such as the bottling units, these receptacles pass through various processing stations, for example through a washing unit, a bottling machine, a labeling machine, even a conditioner, between which stations these receptacles or bottles move by means of conveyors, in particular chain conveyors. In fact, these stations have production rhythms which differ from each other, so that it is necessary, at the level of the intermediate conveying, to form buffer stocks of receptacles, in addition to the fact that some of these stations require more frequent interventions than others. Therefore, in order to avoid, during such intervention, the complete stop of a plant, for example a bottling chain, accumulation tables are provided for, which allow to temporarily store the bottles proceeding from an upstream processing unit, until the end of the intervention and the downstream processing unit is re-started.
For example, from JP-A-61 051415 is known an accumulation table arranged parallel to a single-row conveyor onto which the receptacles arrive one by one. If a jamming occurs in the downstream portion of this single-row conveyor, these receptacles escape laterally on the accumulation table. Through reversing the direction of operation of the chains the latter is comprised of the stored receptacles are anew injected onto the single-row conveyor.
One understands very well that the number of bottles likely to be stored between two stations determines the time available for an operator to ensure his intervention without it being necessary to completely stop the production chain.
In brief, the more receptacles can be accumulated between two successive processing stations, the more flexible will be the use of the conditioning plant.
Obviously, this is not without some concessions. In particular, the conveying units with accumulation prove very bulky, which raises the problem of their integration into a production site where the floor occupation has to be optimized.
If we consider the particular case of an accumulation table of the type as described in WO-00/41955, it has a large capacity of passive accumulation of receptacles. However, its length associated, downstream, with that of a passive aligner for these receptacles, the aim of which is to convey the latter in one single row towards a next processing unit, most often proves too large for this aggregate to find its place in a production chain.
In this respect, though it is usual, in newly installed plants, to integrate, between two successive processing stations, conveying units with accumulation, it is increasingly more often sought to provide also the existing plants with them and, in such a case, the problem set forth above is even more obvious.
Other conveying units with accumulation are also known, which are substantially comprised of two helical conveyors nested into each other, one progressing in one direction and the other one in the opposite direction, while a transfer device is designed capable of ensuring the transfer of the receptacles accumulating on the first conveyor and proceeding from an upstream processing unit towards the second conveyor which feeds a downstream processing unit. This transfer device is capable of progressing alongside the helix between both conveyors depending on the quantity of accumulated receptacles.
The drawbacks of such an embodiment derive from its complexity. In particular, the interventions by an operator prove very difficult. Furthermore, one easily understands that, in order to allow the transfer of a receptacle from one conveyor to another, the latter may not be provided with guiding rails at their communicating lateral sides. Therefore, receptacles often fall down and the speed of progression of the latter is necessarily slow.
These units also have a problem of integration due to their size, not in length, but in width and in height, in addition to the fact that they have an accumulation capacity often much smaller than that of a table of the type as described in WO 00/41955.